Rhododendron PJM Group

For three generations, the Mezitt family in the Weston nursery ^[4] has been engaged in the selection of rhododendrons adapted for cultivation in New England ( frost resistance zone - 5). When conducting this breeding program, special attention is paid to the creation of varieties for landscape use. The story begins with a cross made in 1939 by Ed Mezitt, the son of the founder of the nursery, Peter J. Mezitt. Peter received plants collected by missionaries in the Chinese part of Altai , as it later turned out, R. dauricum var. sempervirens ( R. dauricum Semper-Virens Group). The pollen of this plant, Ed pollinated Rhododendron minus Carolinianum Group ( R. carolinianum ). As a result of the selection of seedlings, a number of varieties of the PJM group were created.

In 1957, a white form of R. carolinianum was crossed with plants of the PJM group. As a result, the varieties Balta and Laurie were obtained. Both varieties have a neat crown shape, are characterized by slow growth and bloom in early May (in zone 5). Flowers depending on the season from pale pink to white ^[5] .

Edmund Mezitt named the group after his father, whose name was Peter John Mezitt ^[1] .

The bush has a compact and neat shape, a height of 120-182 cm (up to 300 cm), a width of about 2/3 of the height ^[2] . According to the manufacturer ( frost resistance zone - 5): height 243 cm, old specimens can reach a height of 457 cm ^[1] .

The bark is gray-brown, smooth.

The leaves are smaller than that of R. carolinianum , elliptical, 3.3-6.3 cm long, dense, dark green (purple-plum (red-violet) in winter), shiny, fragrant when rubbed.

The flowers are bright, pink and lavender. Specific clones have flowers of various shades.

It blooms in mid-late April ^[2] .

` Black Satin` Edmund V. Mezitt, until 1972. At the age of 10 years, the height of the plants is about 90 cm, the width is about 90 cm. The leaves are evergreen, 44 × 19 mm, green, mahogany in winter. Inflorescences are terminal, spherical, bear about 5-10 flowers. Funnel-shaped flowers, 25 × 32 mm, are described as reddish-violet or violet-purple with a coral throat. It withstands winter temperature drops to −29 ° С ^{[6] [7] [8]} .

`Elite` (` PJM Elite`) Mezitt EV, 1939. The variety is registered in 1987. The height of adult plants is about 243 cm, old plants can reach a height of 457 cm. In Finland, at the age of 10 years, the height is about 1.2 m. According to the website of Deutsche Genbank Rhododendron, at the age of 10 years, the height of the plants is about 90 cm, the width is about 100 cm. Height energetic, bush vertical, dense crown. The leaves are elliptical, green, bronze in the winter, 51 × 25 mm. Inflorescences are terminal, spherical, 80 × 65 mm, bear 9-15 flowers. Funnel-shaped flowers, 25 × 38 mm, lavender-pink, blooms later than most varieties of the group. Stamens are white. There is no aroma . It withstands temperature drops of up to −32 ° С, according to some reports up to −35 ° С. Frost resistance zones : from 4 to warmer ^{[9] [10] [11] [12] [2]} . In the conditions of the Nizhny Novgorod region it is completely winter-hardy . Fruits ^[13] .

` Northern Starburst` Briggs Nursery, 1996 - tetraploid form. The bush is compact, at the age of 10 years, height is about 60 cm. The inflorescences are dome-shaped, bear 4-5 flowers. Flowers 40 × 65 mm, wide-funnel-shaped, purple. Shoots and leaves are relatively thick. The leaves are 65 × 30 mm, elliptical, the edges are slightly bent down, in the summer they are dark green, in the winter they are dark, gray-red-brown, 1-2 years remain. Petioles of leaves are scaly, about 5 mm long ^{[2] [14]} .

' Checkmate' (syn. ' PJM Checkmate' ) is a dwarf, slowly growing form. Height at the age of 10-15 years is about 121 cm, old plants can reach a height of 243 cm. The hemispherical crown. The flowers are small, pink-lavender, flowering in the 5th zone at the end of April. Recommended for small gardens where space is limited. This is the most dwarf variety of the group 'PJM'. Mutation 'Victor'. Zones of frost resistance : from 5 to warmer ^[15] .

` PJ Mezitt` blooms with light purple-red flowers in the spring, in Finland in the Mustila arboretum - in mid-May. In ten years, it grows into a dense rounded bush with a height of more than one meter ^[3] , according to another source at the age of 10 years, a height of about 1.2 m. It can withstand temperature drops to −32 ° C, but the buds can be damaged already at −21 ° C after winter thaws ^[16] .

' PJM Compact Form' is a tetraploid. But the real dwarf form. The flowers are relatively large, the leaves are relatively thick. The crown is vertical, dense ^[2] .

` PJM Lavender` - an early flowering half-dwarf, flowers are pale pink. Green foliage turns purplish-brown in winter ^[2] .

' PJM Princess Susan' - a dwarf form, characterized by slow growth, flowers are pale purple ^[2] .

` Regal` - has pale pink flowers, flowering earlier than that of` Elite` (in the middle of the season for the group `PJM`). In Finland, at the age of 10 years, the height is about 1.2 m. Below the 'Elite', although it is characterized by vigorous growth, the crown is more open. It withstands temperature drops to −30 ° C ^{[2] [17]} .

` Victor` - early flowering` PJM`, characterized by relatively slow growth and compactness of the crown ^[2] .

Withstands temperature drops to -32 ° C ^[18] . The root system can withstand temperature drops of -23 ° C ^[19] .

Frost resistance zones : from 4 to warmer ^[1] .

Location: sun, partial shade. In a sunny place, inflorescences cover the entire bush. However, if the plant wakes up too early after winter, buds that are ready to bloom can freeze during spring night frosts. In autumn, part of the leaves is painted in beautiful autumn tones and falls off. At the ends of the branches there are leaves that turn brown with the advent of frost. With the onset of spring, the green color returns to the looking dead leaves ^[3] .

The soil is moist, acidic, well-drained. Compared with other varieties, it has good adaptability to soil characteristics ^[2] .

Landing The optimal diameter of the pit for planting is 60 cm, the depth is 40 cm. The composition of the soil mixture is acidic peat , garden soil ( loam ) and pine litter , taken in equal parts, or 1 part of garden soil, 2 parts of acidic sphagnum peat. High peat can be replaced by sphagnum ^[20] .

• Voronina S. Rhododendrons. The difficult problem of choice (unopened) . Ganov A. .. Date of treatment March 11, 2013. Archived on April 7, 2013.
• Lecture of S. Krivitsky. Culture of rhododendrons in the Moscow Region: the history of introduction, cultivars, agricultural technology.
• James Kohut, Staff Writer. Growing Azaleas And Rhododendrons In The North . Northscaping.com. Date of treatment March 12, 2013. Archived March 16, 2013.